I'm no expert on rewinding transformers but wouldn't the transformer show physical signs of having been taken apart such as laminations having been moved (the label looks intact) and signs of varnish being cracked. The wires in the picture all have that look of originality.
Sorry, the picture was just to show the transformer to JMFahey.
The first time i took it out i have taken that picture.
Right now the transformer has a lot of varnish ( I think thats the name ) and a different wrap around the wires.
I think they didnt charge the repair because it happens the same in a short amount of time.
The first time i took it out i have taken that picture.
Right now the transformer has a lot of varnish ( I think thats the name ) and a different wrap around the wires.
I think they didnt charge the repair because it happens the same in a short amount of time.
Ah, OK. I just wondered. So that was an earlier picture.
So it really does seem the transformer has an underlying issue. The problem may be on the primary winding, it doesn't have to be the secondary that is faulty.
I don't know what to advise you. You could look at primary current draw and see if that showed any issues. Have a waggle of the wires and perhaps connect a very small filament bulb as a secondary load (like a fridge bulb).
So it really does seem the transformer has an underlying issue. The problem may be on the primary winding, it doesn't have to be the secondary that is faulty.
I don't know what to advise you. You could look at primary current draw and see if that showed any issues. Have a waggle of the wires and perhaps connect a very small filament bulb as a secondary load (like a fridge bulb).
I was monitoring the current thru the variac that has a meter. It was stable all the time. The strange thing was that as soon i take the input jack with the signal, the current drop to the normal value at idle and after some seconds as increased and the HT voltage as drop.
I think im going to try and get a new one from Koch.
They havent reply to mail emails but i will try again.
Then i will check again the circuit.
I think im going to try and get a new one from Koch.
They havent reply to mail emails but i will try again.
Then i will check again the circuit.
It's preferable to check the circuit first before connecting a new and healthy PT to it.
Best regards!
Best regards!
I have talk to them ( koch ) on the phone. They said its very strange. Its not a usual thing like this to happen
except for the voltage readings your idle currents seem normal to me...
here is what you can do...and so give us a better understanding...
1. disconnect all secondaries from the circuit.
2. apply voltage to the primary side.
3. measure all secondary voltages and compare that to the specs of the traffo
then tell us what you find...a 0.26a idle current seems normal,
in order to avoid wires being connected the wrong way, i take photos of the amp as is, that way i can always go back to the way it was before...
your 12ax7's pull very little current so that the 500 ohm dc resistance you mentioned did not bother me much..
here is what you can do...and so give us a better understanding...
1. disconnect all secondaries from the circuit.
2. apply voltage to the primary side.
3. measure all secondary voltages and compare that to the specs of the traffo
then tell us what you find...a 0.26a idle current seems normal,
in order to avoid wires being connected the wrong way, i take photos of the amp as is, that way i can always go back to the way it was before...
your 12ax7's pull very little current so that the 500 ohm dc resistance you mentioned did not bother me much..
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yes they do....resistance varies, high voltage low current have much higher resistance than windings for filaments...
Not sure what "servicing" mens to them but that transformer has NOT repeat NOT been rewound within the last couple of years (or more).
Rewinding requires pulling laminations.
Paint bubbles, rust patches and quarter coin glue patch on top left corner show those laminations have not been removed, so it has not been rewound.
Most they might have done is cutting some fishpaper open and resoldering some iffy enamelled wire to PVC insulated output wire ... but I am not sure even of that intervention.
Please show the brown paper side of transformer.
That.
I bet Osvaldo, being an Engineer, already knows that 😉
I think his is a specific question (demanding measurements) to the OP who actually has the transformer (and the problem) in his hands.
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Im going to take some pictures as soon i take it out.
I really want to know your opinion...
It as been rewond or not?
IMHO, that is a small piece of iron, even for a SE 45 amp. Also, I fully agree with the assessment that it has not been rewound.
If it were just one OT, then it would make sense, but such a small power transformer? No surprise if a secondary gets easily overloaded.
The brown paper appears fairly "new"...
If it were just one OT, then it would make sense, but such a small power transformer? No surprise if a secondary gets easily overloaded.
The brown paper appears fairly "new"...
IMHO and per ante/post comparison, this xformer has at least been dismantled. Look at the disrupted lacquer structure, and it also appears that the label has been stripped off.
I'm not sure, though, why the shop hasn't been able to rewind it properly. Winding a power tranny isn't rocket science at all!
Best regards!
I'm not sure, though, why the shop hasn't been able to rewind it properly. Winding a power tranny isn't rocket science at all!
Best regards!
I agree with J.M. This traffo hasn't been disassembled and then, is not repaired at all, Surely the "repairmen" injected a small quantity of any insulating liquid between the layers (Oil, varnish) and expect that this would save the traffo. I believe you were cheated and I would claim for the warranty (if any and with many lucky).
i found this esr tester very useful in testing chokes ad traffos,
a good coil will have both resistance and inductance at the same time,
a bad coils otoh, the one with an adjacent turn shorts will register as just a resistance with no inductance....
YouTube
i make my own power and output traffos and to be honest it is not going to be fair to judge from pictures alone....
from where are you by the way?
defective equipment have at least a 1 year warranty, some evenmore, so when i get repair inquiries, that is the first thing i would ask, what is the RMA like? RMA, return merchandise agreement......
i will never recommend any equipment under warranty to be opened up, that voids the warranty and will cost you more money to repair...
if you can not trust your repair techs? who can you trust? men behind the pc monitors?
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shouldn't you be looking as to why this happened? because you can send the traffo n times and n times you may still have a problem, if i were you, i would start investigating as to why that happened in the first place and not keep banging on the traffo rewind....if you have problem elsewhere you will always have your trafo shot...